The present invention relates to a rongeur, and more particularly to a rongeur having a detachable crossbar.
The rongeur is a medical instrument used for a variety of purposes. It is particularly useful for removing small amounts of bone, cartilage or other body material from inside small spaces of the knee or between vertebrae. A rongeur usually includes a long fixed shank with an anvil or footplate at its distal end and a handle at its proximal end. A cross bar slideably engages the shank and reciprocates thereon by means of a pivotable second handle. Cutting edges on the distal end of the crossbar bite against the footplate to cut away a small portion of tissue with each reciprocation of the crossbar.
For precise operation of the instrument tight tolerances between the mating parts is preferred. While enhancing precise operation, these tolerances can make effective cleaning of the instrument difficult. Blood and other bodily matter with becomes trapped between the shank and crossbar can be difficult to remove. Failure to remove such matter can lead to incomplete sterilization. Accordingly, it is desirable to allow access to these parts during cleaning and sterilization.
The Janzen U.S. Pat. No. 6,126,674, incorporated herein by reference, attempts to solve this problem by providing a removable crossbar. A slot in the top of the pivotable handle receives a pin on the crossbar. A rotating disc on the fixed handle abuts a surface on the pivotable handle to limit spread between the handles. Rotation of the disc into an alternate orientation allow a slightly broader spread between the handles allowing the crossbar to move back distally off of the pin and to then be removed. In such a design it can be difficult to balance the force necessary to rotate the disc. If the force required is too great it can be difficult to operate and discourage disassembly prior to sterilization. If the force required is too low it can allow the device to disassemble accidentally during normal use.
A rongeur according to the present invention overcomes these and other limitations of the prior art. It comprises an elongated shank having a distal end and a proximal end and an elongated crossbar having a distal end and a proximal end adapted to reciprocate axially with respect to the shank. The crossbar has a retracted position wherein the crossbar is partially retracted proximally with respect to the shank and a retracted-release position wherein the crossbar is further retracted proximally with respect to the shank than in the retracted position. Mating surfaces on the shank and crossbar align to block disengagement of the crossbar from the shank in the retracted positions and come out of alignment to allow disengagement of the crossbar from the shank in the retracted-release position. A first handle is fixedly configured to the shank proximal end and a second handle pivotably attaches to the shank proximal end about a pivot axis. A slot in an upper portion of the second handle receives a pin affixed to the crossbar at its proximal end whereby pivoting of the second handle about the pivot axis induces axial movement of the pin to reciprocate the crossbar. Engagement between the pin and the slot prevents the crossbar from retracting to the retracting-release position. The pin is selectively moveable upwardly sufficiently out of the slot to allow further proximal movement of the crossbar with respect to the shank to the retracted-release position whereby to allow the crossbar to be disengaged and removed from the shank for more effective cleaning and sterilization thereof.
Preferably the mating surfaces comprise an undercut slot on one of the shank and crossbar and a flange on the other of the shank and crossbar received within the slot, and more preferably the slot and flange are T-shaped. Preferably, a proximal portion of the slot is not undercut.
Preferably, the pin is positioned on a holding member on the crossbar, the holding member having a first position in which the pin is sufficiently deeply within the slot to prevent retraction of the crossbar to the retracted-released position and a second position in which the pin is sufficiently out of the slot so as to allow retraction of the crossbar to the retracted-release position. Preferably, a detent engagement is provided between the holding member and the crossbar when the holding member is in its first position, which engagement can comprise a spring ball. In one aspect of the invention, the holding member has a U-shaped cross section and is received over the crossbar. The pin can penetrate an aperture on the crossbar to fix the holding member to the crossbar. Preferably, the crossbar has a vertical groove and the holding member has a rib on an inner surface thereof which slides within the vertical groove.
Preferably, one or more of drainage apertures penetrate through the shank adjacent the footplate. The drainage apertures can penetrate through the shank at the slot.